The invention relates to a slip ring unit of a rotor of an electrically excited rotary dynamo-electric machine, the rotary dynamo-electric machine, and its application in generators of wind power installations.
Various designs of rotary dynamo-electric machines are known, in particular for use as wind power generators. These include a design in which a winding of the rotor is electrically supplied via slip rings. The currents of the rotors of these wind power generators must be led away from the winding of the rotor and linked to the slip ring unit. Litz wires with comparatively large cross sections greater than 90 mm2 are used for this purpose.
Owing to the increasing runaway speeds of the rotors, the danger now exists that the terminal bolts of the slip ring unit may be damaged or work loose in their seating due to the centrifugal stress caused by the free mass of these litz wires. The consequence would be significant damage and/or failure of the generator and comparatively high repair costs.
Owing to the high current strengths, such cross sections of litz wires are now required in order to provide the electrical current carrying capacity. Therefore the now freely rotating masses are comparatively high and can no longer be ignored. In this case, use is customarily made of an end-lead bushing which has three copper profiles and provides a rigid down conductor in the interior of the shaft, connecting the winding of the rotor to the respective slip ring via stud bolts and flexible copper laminated strips. This has disadvantages with regard to the expense of high-current bushing and the significant cost of maintenance in the event of failure.